Background Elucidating the phylogenetic relationships within species-rich genera is essential but challenging, especially when lineages are assumed to have been going through radiation events. Mahonia Nutt. (Berberidaceae) is a genus with cosmopolitan distribution, comprising approximately 100 species, two of which are known as Caulis Mahoniae (M. bealei and M. fortunei) with crucial pharmacological significance in Chinese herbal medicine. Mahonia is a taxonomically challenging genus, and intrageneric phylogenetic relationships still need to be explored using genome data. Universal DNA barcodes and floral morphological attributes have limited discriminatory power in Mahonia. Results We sequenced 17 representative plastomes and integrated three published plastome data together to conduct comparative and phylogenetic analyses. We found that Mahonia and Berberis share a large IR expansion (~ 12 kb), which is recognized as a typical character of Berberideae. Repeated sequences are revealed in the species of Mahonia, which are valuable for further population genetic studies. Using a comparative plastome analysis, we determined eight hypervariable regions whose discriminative power is comparable to that of the whole plastid genomes. The incongruence of the ITS and the plastome tree topologies may be ascribed to ancestral hybridization events and/or to incomplete lineage sorting. In addition, we suggest that leaf epidermal characters could help to distinguish closely related species in Mahonia. Conclusions We propose an integrative approach combining special barcodes and micromorphological traits to circumscribe Mahonia species. The results cast a new light on the development of an integrative method for accurate species circumscription and provide abundant genetic resources for further research on Mahonia.

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Subfamily Nandinoideae Heintze (Berberidaceae), comprising four genera and ca. 19 species, is disjunctively distributed in eastern North America vs. Eurasia (eastern Asia, Central Asia, Middle East, and southeastern Europe), and represents an ideal taxon to explore plastid phylogenomics and plastome evolution in Berberidaceae. Many species of this subfamily have been listed as national or international rare and endangered plants. In this study, we sequenced and assembled 20 complete plastomes, representing three genera and 13 species of Nandinoideae. Together with six plastomes from GenBank, a total of 26 plastomes, representing all four genera and 16 species of Nandinoideae, were used for comparative genomic and phylogenomic analyses. These plastomes showed significant differences in overall size (156,626-161,406 bp), which is mainly due to the expansion in inverted repeat (IR) regions and/or insertion/deletion (indel) events in intergenic spacer (IGS) regions. A 75-bp deletion in the ndh F gene occurred in Leontice and Gymnospermium when compared with Nandina and Caulophyllum . We found a severe truncation at the 5' end of ycf 1 in three G. altaicum plastomes, and a premature termination of ropC 1 in G. microrrhynchum . Our phylogenomic results support the topology of { Nandina , [ Caulophyllum , ( Leontice , Gymnospermium )]}. Within the core genus Gymnospermium , we identified G. microrrhynchum from northeastern Asia (Clade A) as the earliest diverging species, followed by G. kiangnanense from eastern China (Clade B), while the rest species clustered into the two sister clades (C and D). Clade C included three species from West Tianshan ( G. albertii , G. darwasicum , G. vitellinum ). Clade D consisted of G. altaicum from northern Central Asia, plus one species from the Caucasus Mountains ( G. smirnovii ) and three from southeastern Europe ( G. odessanum , G. peloponnesiacum , G. scipetarum ). Overall, we identified 21 highly variable plastome regions, including two coding genes ( rpl 22, ycf 1) and 19 intergenic spacer (IGS) regions, all with nucleotide diversity ( Pi ) values > 0.02. These molecular markers should serve as powerful tools (including DNA barcodes) for future phylogenetic, phylogeographic and conservation genetic studies.

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The early-diverging eudicot family Berberidaceae is composed of a morphologically diverse assemblage of disjunctly distributed genera long praised for their great horticultural and medicinal values. However, despite century-long studies, generic delimitation of Berberidaceae remains controversial and its tribal classification has never been formally proposed under a rigorous phylogenetic context. Currently, the number of accepted genera in Berberidaceae ranges consecutively from 13 to 19, depending on whether to define Berberis , Jeffersonia , and Podophyllum broadly, or to segregate these three genera further and recognize Alloberberis , Mahonia , and Moranothamnus , Plagiorhegma , and Dysosma , Diphylleia , and Sinopodophyllum , respectively. To resolve Berberidaceae's taxonomic disputes, we newly assembled 23 plastomes and, together with 85 plastomes from the GenBank, completed the generic sampling of the family. With 4 problematic and 14 redundant plastome sequences excluded, robust phylogenomic relationships were reconstructed based on 93 plastomes representing all 19 genera of Berberidaceae and three outgroups. Maximum likelihood phylogenomic relationships corroborated with divergence time estimation support the recognition of three subfamilies Berberidoideae, Nandinoideae, and Podophylloideae, with tribes Berberideae and Ranzanieae, Leonticeae and Nandineae, and Podophylleae, Achlydeae, Bongardieae tr. nov. , Epimedieae, and Jeffersonieae tr. nov . in the former three subfamilies, respectively. By applying specifically stated criteria, our phylogenomic data also support the classification of 19 genera, recognizing Alloberberis , Mahonia , and Moranothamnus , Plagiorhegma , and Diphylleia , Dysosma , and Sinopodophyllum that are morphologically and evolutionarily distinct from Berberis , Jeffersonia , and Podophyllum , respectively. Comparison of plastome structures across Berberidaceae confirms inverted repeat expansion in the tribe Berberideae and reveals substantial length variation in accD gene caused by repeated sequences in Berberidoideae. Comparison of plastome tree with previous studies and nuclear ribosomal DNA (nrDNA) phylogeny also reveals considerable conflicts at different phylogenetic levels, suggesting that incomplete lineage sorting and/or hybridization had occurred throughout the evolutionary history of Berberidaceae and that Alloberberis and Moranothamnus could have resulted from reciprocal hybridization between Berberis and Mahonia in ancient times prior to the radiations of the latter two genera.

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The first complete chloroplast genome (cpDNA) sequence of Pericampylus glaucus was determined from Illumina HiSeq pair-end sequencing data in this study. The cpDNA is 162,450 bp in length, contains a large single-copy region (LSC) of 90,871 bp and a small single-copy region (SSC) of 21,137 bp, which were separated by a pair of inverted repeats (IR) regions of 25,221 bp. The genome contains 130 genes, including 85 protein-coding genes, 8 ribosomal RNA genes, and 37 transfer RNA genes. The overall GC content of the whole genome is 38.0%, and the corresponding values of the LSC, SSC, and IR regions are 36.2, 32.1, and 43.5%, respectively. Further, phylogenomic analysis showed that P. glaucus and Stephania japonica clustered in a clade in family Menispermaceae.

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The history of the Red List of Japanese vascular plants is briefly reviewed for editing and research. Especially on the results of recent monitoring, the present status of information and conservation activities on the endangered plants in Japan is discussed and the dynamics of the Japanese flora are taken up, in relation to basic research on plant biodiversity on the Japanese Archipelago. The figures of endangered plants are not very variable during the past quarter of a century, but we can surmise that the conservation of threatened species in Japan has been promoted to some extent. Based on the results of such a study, proposals are made to contribute to the sustainable use of plant biodiversity on the Japanese Archipelago under a global conspectus.

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